Elusive Nature of Entropy, Nature of Thermal and Mechanical Energy Transfer and Reflections on the Caloric Theory and Thermal Energy. * Feynman's Lecture
"Entropy is associated with stored-heat within a material system, i.e. its thermal energy. It is an integral measure of thermal energy per absolute temperature of a system (transferred as heat into and generated heat within, due to work potential dissipation to thermal heat). As heat is generated due to dissipation of any work potential to heat, the entropy is irreversibly produced. However, if heat is converted to work (like in heat engines), the thermal energy is reduced while transferred to a lower-temperature thermal reservoir, however, the entropy (as ratio of thermal heat to absolute temperature) will not be reduced but conserved in ideal, reversible processes (Qrev/T=const, Carnot Ratio Equality), or even the entropy will be produced (generated) in real (irreversible) processes for the amount of dissipated work-potential to stored heat (or thermal energy) per absolute temperature, regardless that the thermal energy is reduced (converted to work). Therefore, the entropy is always produced, locally and thus integrally or globally, and there is no way to destroy entropy, since it will be against the forced energy transfer from higher to lower potential [Kostic 2011 & 2014]."
PPS: We are aware that the thermal phenomena are elusive and coupled with other energy forms.
I am working to decouple thermal, from other internal forms of energies, where the "caloric heat transfer processes" (only heating/cooling with full dissipation of work potential) and "reversible heat transfer" (with extraction of full Carnot work potential) are two extreme cases (the former fully dissipates work-potential, while the latter fully extracts-and-utilize it). A reasonable physical intuition has an advantage over "blind" analytics. For example, intuitively the change of Exergy should not depend on value of reference dead state (Po,To), even though the Exergy does, and analytics may misguide the physicality. For example:
Exergy of heat Q1 at temperature T1 is Ex1=Q1(1-To/T1) and for state 2 would be Ex2=Q2(1-To/T2), so:
Ex1-Ex2=Q1(1-To/T1) - Q2(1-To/T2), as if it is a function of To.
However, for Exergy, i.e., the reversible work potential, the Q2/T2=Q1/T1, the relevant quantities are correlated, so the above is reduced to:
Ex1-Ex2=Q1(1-To/T1) - (Q1T2/T1)(1-To/T2)=(Q1/T1)(T1-T2), thus NOT function of To!
The similar applies in general where internal energy U is used, since relevant U2 is correlated to U1 etc... *Irreversible-Reversible Equilibrium
This is Prof. Kostic's Web site being transitioned from the original or Legacy Web(*) - sorry for broken links referring to it!